How heavy is the car and what's the effective 1st gear ratio?
A very light flywheel in a heavy car with a tall effective first gear ratio can be very tricky to get moving... there is a fine line between slipping it too much or killing it (or going up in smoke if you like to do that in town... LOL)
That being said I prefer flywheels on the lighter side of the spectrum. I currently run a 20# billet steel flywheel and am quite happy with it. I would like to try one of the 3 or 4 puck small diameter clutch/flywheel combos but they're big bucks and I could use the money elsewhere right now. My car is at 3950# with me in it and a full tank of gas, and I run an older TKO (3.27 first) with 3.42 rear gears. I find it a piece of cake to launch with the 20# flywheel but it never fails--
every time I've let someone else try and drive it they kill it taking off, usually 6-10 times. Heck, my buddy with an alignment shop couldn't even get it on his rack and after 3 tries he got out and said "you do it."
